AUTHOR=Karlsson Øyvind , Gilgien Matthias , Gløersen Øyvind N. , Rud Bjarne , Losnegard Thomas 

TITLE=Exercise Intensity During Cross-Country Skiing Described by Oxygen Demands in Flat and Uphill Terrain

JOURNAL=Frontiers in Physiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.00846

DOI=10.3389/fphys.2018.00846

ISSN=1664-042X

ABSTRACT=<p><bold>Purpose:</bold> In this study wearable global navigation satellite system units were used on athletes to investigate pacing patterns by describing exercise intensities in flat and uphill terrain during a simulated cross-country ski race.</p><p><bold>Methods:</bold> Eight well-trained male skiers (age: 23.0 ± 4.8 years, height: 183.8 ± 6.8 cm, weight: 77.1 ± 6.1 kg, VO<sub>2peak</sub>: 73 ± 5 mL⋅kg<sup>-1</sup>⋅min<sup>-1</sup>) completed a 13.5-km individual time trial outdoors and a standardized indoor treadmill protocol on roller skis. Positional data were recorded during the time trial using a differential global navigation satellite system to calculate external workloads in flat and uphill terrain. From treadmill tests, the individual relationships between oxygen consumption and external workload in flat (1°) and uphill (8°) terrain were determined, in addition to VO<sub>2peak</sub> and the maximal accumulated O<sub>2</sub>-deficit. To estimate the exercise intensity in the time trial, the O<sub>2</sub>-demand in two different flat and five different uphill sections was calculated by extrapolation of individual O<sub>2</sub>-consumption/workload ratios.</p><p><bold>Results:</bold> There was a significant interaction between section and average O<sub>2</sub>-demands, with higher O<sub>2</sub>-demands in the uphill sections (110–160% of VO<sub>2peak</sub>) than in the flat sections (≤100% of VO<sub>2peak</sub>) (<italic>p</italic> &lt; 0.01). The maximal accumulated O<sub>2</sub>-deficit associated with uphill treadmill roller skiing was significantly higher compared to flat (6.2 ± 0.5 vs. 4.6 ± 0.5 L, <italic>p</italic> &lt; 0.01), while no significant difference was found in VO<sub>2peak</sub>.</p><p><bold>Conclusion:</bold> Cross-country (XC) skiers repeatedly applied exercise intensities exceeding their maximal aerobic power. ΣO<sub>2</sub>-deficits were higher during uphill skiing compared to flat which has implications for the duration and magnitude of supramaximal work rates that can be applied in different types of terrain.</p>